This invention relates to inverters useful in interfacing dc energy sources to a utility grid.
Experimental systems to date have used line commutated inverters or uninterruptable power supplies for performing the task of extracting power from a dc source such as a photovoltaic array or a battery and injecting the power into an ac utility. The line commutated inverters, while inexpensive, suffer from (a) poor power factor which may upset the system regulation and/or increase the necessary rating of the transmission equipment and (b) high harmonic currents which can increase losses in motors, capacitors and transmission equipment and interfere with computers and communication equipment. The uninterruptable power supply while maintaining sinusoidal output wave shapes are too expensive for residential applications.
It is an object of the present invention to extract power from a dc source and convert the power such that sinusoidal current is injected into a utility power source at near unity power factor.
It is a further object of the present invention to accomplish the power conversion in an energy efficient and inexpensive manner.